The subject matter disclosed herein relates generally to apparatuses and methods for retaining fluid lubricant, such as oil, in an oil sump and/or its drain path. More specifically, but not by way of limitation, some example embodiments relate to apparatuses and methods for maintaining design gaps during axial excursions of a shaft while also improving the limitation of oil leakage, for example from in a sump of a turbine engine.
In a turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine includes a first stage nozzle and a rotor assembly including a disk and a plurality of turbine blades. The high pressure turbine first receives the hot combustion gases from the combustor and includes a first stage stator nozzle that directs the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from the first rotor disk. In a two stage turbine, a second stage stator nozzle is positioned downstream of the first stage blades followed in turn by a row of second stage turbine blades extending radially outwardly from a second rotor disk. The stator nozzles turn the hot combustion gas in a manner to enhance extraction at the adjacent downstream turbine blades.
The first and second rotor disks are joined to the compressor by a corresponding high pressure rotor shaft for powering the compressor during operation. The high pressure turbine powers rotation of the compressor to create compressed air for combustion, thus continuing the process. A multi-stage low pressure turbine follows axially the two stage high pressure turbine and is typically joined by a second shaft coaxial with the first shaft to a fan disposed upstream from the compressor in a typical turbo fan aircraft engine configuration for powering an aircraft in flight.
As the combustion gasses flow downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced while providing fan rotation for aviation thrust. Alternatively, the combustion gas is used to power the compressor and a turbine output shaft for power and marine use. In this manner, fuel energy is converted to mechanical energy of the rotating shaft to power the compressor and supply compressed air needed to continue the process.
During rotation of the core of the turbine engine, and at some operating temperatures, axial excursions of the rotor shaft and parts connected thereto may sometimes occur. Seal teeth structures have been used to seal areas of differential pressure or oil and air and maintain pressure for pressurized seals. Ensuring that a design gap over a discourager tooth is always maintained during these axial excursions often required extending the opposed sealing surface, which could be problematic to the design of surrounding components.
Of additional concern, at some operational design altitudes, for example 51,000 feet, air is of very low density. Such thin air may not have enough force against the direction of oil seals so as to fully inhibit leakage from the sump.
The problems: Oil leakage across seals may be disadvantageous for a turbine engine. Axial excursions of the rotor and connected structures may cause an associated sealing structure to lose a design or seal gap with an opposed land. In some oil sump configurations, excessive pressure differential around an oil sump may cause undesirable oil leakage.